Alcohol Myopia (AM) theory is one of the best explanations of how alcohol leads to risky social behaviors such as unsafe sex, crime, and violence. In AM theory, two cognitive mechanisms are assumed to be pharmacologically disrupted by alcohol: (a) attention, and (b) the ability to inhibit responses. Evidence used to support the AM theory, has focused on social behaviors and self-rated feelings of anxiety. Although these phenomena are relevant to understanding risky behavior, the core assumptions about how alcohol affects attention and the ability to inhibit responses have not been sufficiently tested. Expectancy theory, for example, explains the same social behaviors without reference to either of the alleged pharmacological effects on cognitive processing. The present study examines how attention and inhibition vary across the dose response curve to test the cognitive assumptions of the AM theory and to improve prediction of risky behavior over time. The effects of alcohol on attention will be studied by examining how the speed-accuracy tradeoff function changes in response to low and moderately high doses of alcohol. The speed-accuracy tradeoff function is a measure of cognitive efficiency that has been used to detect effects of alcohol when comparisons of mean reaction times and error rates have produced null results. In the proposed experiments, the best methods currently available for assessing the speed-accuracy tradeoff will be used to track alcohol- related changes in cognitive efficiency. Subjects will be asked to perform a choice reaction time task that either requires or does not require attention. The AM theory is contrasted with a Rate Reduction theory in which alcohol is predicted to produce a general slowing of cognitive processing, but to have no specific effect on attention. The pharmacological effects of alcohol on the ability to inhibit responses will be examined by using the Stop Signal Technique (SST). In the SST, subjects are asked to perform a choice reaction time task, but to try to inhibit their responses whenever they hear a tone (stop signal). By varying the lag time between the presentation of a stimulus that is to be classified and the time the stop signal sounds, an estimate of cognitive stopping time can be derived. AM theory predicts that cognitive stopping time will increase as a function of the pharmacological dose, whereas, Expectancy theory predicts an increase in cognitive stopping time based on the amount of alcohol subjects think they have consumed. The expected and pharmacological effects of alcohol will be dissociated at socially relevant levels of drinking by employing the Extended Balanced Placebo Design (EBPD: Lapp et al., In Press-b). The EBPD improves upon previous investigations which were limited to low doses of alcohol and did little to track changes due to fluctuating blood alcohol levels. By contrasting predictions of AM and Expectancy theories, the proposed research will expand our understanding of the processes that underlie cognitively-based theories of social behavior.